Methods and systems for deploying seismic devices

ABSTRACT

Methods and systems for acoustically determining reservoir parameters of subterranean formations. A tool comprising at least one seismic source or seismic receiver mounted thereon; a conveyance configured for movement of the acoustic tool in a borehole traversing the subterranean formations; and a source retainer configured or designed for permanent deployment in the borehole to removably retain the acoustic tool in the borehole. The source retainer when deployed provides acoustic coupling with the borehole and removably retains the acoustic tool in the borehole so that, over multiple deployments, the acoustic tool is repeatedly deployed at the same predetermined location and orientation relative to the subterranean formation, and with the same acoustic coupling to the borehole.

This application is a divisional application of co-pending U.S. patentapplication Ser. No. 12/364,519, filed on Feb. 3, 2009, the content ofwhich is incorporated herein by reference for all purposes.

BACKGROUND

1. Field of the Invention

The present disclosure relates generally to methods and systems forperforming acoustic measurements of subterranean formations. Morespecifically, some aspects disclosed herein are directed to methods andsystems for deploying seismic devices, such as seismic sources and/orreceivers, in a borehole for characterizing subterranean formationshaving, for example, oil and/or gas deposits therein. The methods andsystems utilize permanent downhole installations that removably retainretrievable seismic tools having one or more seismic instrumentationsuch that the seismic instrumentation has a fixed location andorientation relative to the subterranean formations.

2. Background of Related Art

Seismic exploration can provide valuable information useful in thedrilling and operation of oil and gas wells. Seismic measurements of thetype described herein are also useful in the fields of CO₂sequestration, development of methane hydrate deposits, water reservoirmonitoring, microearthquake monitoring, and monitoring for reservoirdelineation, among other applications that are known to persons skilledin the art. Seismic measurements are conducted with energy that isintroduced by a seismic source to create a seismic signal thatpropagates throughout the subterranean formation. This seismic signal isreflected to differing degrees by features that are of interest. Areceiver monitors these reflected signals to help generate a seismic mapof the underground features. This map is generated by knowing the exacttime that a seismic signal was generated as compared to the time thatthe reflected signal is received. As a practical matter, the systemcomprises a plurality of sources and receivers to provide the mostcomprehensive map possible of subterranean features. Differentconfigurations may yield two dimensional or three dimensional resultsdepending on their mode of operation.

In typical seismic exploration, it is necessary to cover a large surfacearea where the deposits of interest, such as oil and/or gas, arelocated. Since productivity is key for this business, the seismicdevices, such as the source(s) and receiver(s) and associatedelectronics, are moved to different locations to cover the area ofinterest. In this, such seismic surveying operations require efficientand fast acquisition of seismic measurements.

Long term monitoring in contrast is geared towards the periodicmonitoring of seismic events and/or the slow movement of fluids in asubterranean reservoir. A reservoir extends over a limited area.Typically the length of data acquisition time is less of a constraint.In this, small changes in the reservoir are detected using, for example,time lapse techniques. Seismic data acquisition is governed by thetiming of the seismic events or changes in the reservoir. Small changesin seismic wave reflection are detected by locating the seismic devices,such as the source and receiver, at the same position with the sameorientation relative to the subterranean formations, and the samecoupling condition. However, an instrument has limited life andeventually it fails. If the instrument is retrieved from its deployedposition, for example, for maintenance, it is not possible to easilyre-deploy the instrument at the same location, in the same orientationand with the same coupling condition. This poses a problem in long termmonitoring operations.

In a typical seismic survey operation utilizing, for example, vibroseissources, large vibrator trucks are deployed to introduce seismic energyinto the subsurface for purposes of reservoir imaging. Such systems arevery large in size and costly. Impulsive sources such as an airgun ordynamite provide a large amount of seismic energy instantaneously for arelatively short duration of time, typically in the order of a fewhundred milliseconds. In contrast, a vibrator provides low seismicpower, but sweep time is comparatively long, typically 20 to 30 seconds.Hence, the total amount of energy that is generated is the same for thetwo types of source devices.

As mentioned above, typically fast data acquisition is not a factor inrelation to permanent sources with fixed receivers that are used in, forexample, reservoir monitoring. Data acquisition may extend for one houror more. Therefore, it is practical to deploy a small seismic sourcedownhole for purposes of seismic surveying by using the source for asuitable length of time to generate the appropriate amount of seismicenergy.

Table 1 below shows an order of magnitude comparison of the differenttypes of seismic sources discussed in the preceding.

P [W] t [sec] E [J] Airgun 1000 0.2 200 Vibrator 10 20 200 Permanentsource 0.1 3600 360

In view of the foregoing, the applicants recognized that it would beadvantageous to deploy downhole seismic devices in a manner that is mostcost efficient and reliable for purposes of long term seismicmonitoring. Applicants discovered that it is possible to utilize acompact seismic source system that is deployable in a borehole forpurposes of seismic surveying. However, seismic sources needcomprehensive maintenance and support. Therefore, conventional seismicsources are often not suitable for permanent or semi-permanentdeployment to monitor subsurface reservoirs.

Alternative seismic energy sources such as airguns and dynamite also areknown in the art. However, in certain applications, such as activepermanent monitoring, the aforementioned seismic energy sources haveshortcomings such as safety, size, cost, required maintenance,repeatability, and environmental impact.

The applicants further recognized that it is advantageous to haveretrievable seismic devices, such as seismic sources and receivers, fordownhole use. Available downhole seismic instrumentation tends to befragile and may not last for an extended period of time without periodicmaintenance. Downhole seismic instruments are expensive, and it iswasteful to permanently deploy them in a borehole if their use islimited. It is preferable to retrieve the seismic devices after aseismic surveying operation and to redeploy the devices when needed forseismic surveying. In this way, the same seismic devices may be deployedat different wellsite so that overall costs and depreciation arereduced. However, when redeployed at a previous wellsite it is necessarythat the seismic devices be located at the same position, in the sameorientation, and with the same coupling condition as the previousseismic operation.

There is need for improved methods and systems for deploying seismicdevices for purposes of acoustically monitoring subterranean formationsto derive key parameters relating to the formations. Specifically, thereis need for techniques for deployment of seismic sources and receiversin a safe manner with low environmental impact for purposes such asactive or passive monitoring with high repeatability. For example, it isdesirable to deploy seismic devices at transition zones, such as at aswamp or shallow water lake/sea, by anchoring or latching the devices inthe hole.

In this, one object of the present disclosure is to provide an improvedmechanism for deployment of downhole seismic sources and receivers.Another object of the present disclosure is to enable deployment ofseismic devices by anchoring in a well or a hole for seismicacquisition.

SUMMARY OF THE DISCLOSURE

The disclosure herein may meet at least some of the above-describedneeds and others. In consequence of the background discussed above, andother factors that are known in the field of formation analysis,applicants recognized need for methods and systems for deploying seismicdevices downhole for purposes of acoustically monitoring subterraneanformations in a reliable, efficient manner with high repeatability. Inthis, applicants recognized that a deployment mechanism was needed thatcould position a seismic source device or a seismic receiver device in aborehole at a constant position for active monitoring of subterraneanformations over extended periods of time.

Additionally, applicants recognized a need for seismic source devicesthat generate seismic signals efficiently with repeatability, and havesuitable source bandwidth, for example, low frequency acoustic energyfor deep imaging. Additionally, applicants recognized that the abilityto remove seismic devices from the downhole locations and to return themto the original position(s) provides significant advantages insemi-permanent/permanent reservoir monitoring operations.

Some of the methods and systems disclosed herein are directed at thedeployment of seismic mechanisms using technologies proposed herein tomonitor key reservoir parameters in relation to the production of oiland/or gas.

In one aspect of the present disclosure, a system for taking acousticmeasurements relating to subterranean formations comprises an acoustictool having at least one of a seismic source and a seismic receivermounted thereon; a conveyance configured for movement of the acoustictool in a borehole traversing the subterranean formations; a toolretainer configured or designed for permanent deployment in the boreholeand, when deployed, being acoustically coupled to the borehole toremovably retain the tool in the borehole so that the tool is deployedat a predetermined location and orientation relative to the subterraneanformations; a computer in communication with the acoustic tool; and aset of instructions executable by the computer that, when executed,process the acoustic measurements; and derive parameters relating to theformation based on the acoustic measurements.

In one embodiment of the present disclosure, the acoustic tool and thetool retainer are configured or designed such that the acoustic tool isdeployed in or removed from the tool retainer by the downward or upwardmovement of the acoustic tool by the conveyance. In certain aspectsherein, the tool comprises a housing, and a plurality of standoffs and awedge located on the outside of the housing. In some embodiments, threestandoffs are provided to effectively stabilize the tool in the boreholeand to provide acoustic coupling with the borehole. The tool retainercomprises a slide and a groove. The plurality of standoffs of the toolhousing are structured and arranged to contact the slide of the toolretainer as the tool is lowered in the borehole such that at least oneof the standoffs locks into the groove of the tool retainer so that thetool is deployed at a predetermined location and orientation relative tothe subterranean formations. The tool retainer may be configured ordesigned to be located at the bottom of a borehole casing.

In other embodiments of the present disclosure, the tool comprises threestandoffs and a spring-actuated locking arm located on the outside ofthe tool housing; and the tool retainer comprises a slide and a groovelocated on an inner surface of a borehole casing joint, wherein the toollocking arm is structured and arranged to be extendible to contact theslide of the casing joint as the tool is lowered in the borehole so thatthe locking arm locks into the groove of the casing joint such that thetool is stabilized and is locked to the borehole casing by theengagement of the tool locking arm and the casing joint groove to deploythe tool at a predetermined location and orientation relative to thesubterranean formations.

In yet other embodiments, the system comprises an array of acoustictools wherein each acoustic tool comprises three standoffs and aspring-actuated locking arm located on the outside of the tool housing;and the tool retainer comprises a plurality of borehole casing joints.Each casing joint has a slide and a groove located on an inner surfaceof the casing joint, wherein the tool locking arm of each acoustic toolis structured and arranged to be extendible to contact the slide of acorresponding one of the plurality of borehole casing joints as the toolarray is lowered in the borehole so that the locking arm of eachacoustic tool locks into a corresponding groove of one of the pluralityof casing joints such that each tool of the acoustic tool array isstabilized and is locked to the borehole casing to deploy each tool ofthe tool array at a predetermined location and orientation relative tothe subterranean formations. Sections of the conveyance between adjacenttools of the acoustic tool array have slack to prevent acousticpropagation between tools through the conveyance. In other words, theseparation between the tools in an array is longer than the separationbetween the casing joints that are designated for receiving theindividual tools in the array. The cable length between adjacent toolsin the array is slightly longer, for example, 5% longer, than theseparation between adjacent designated casing joints so that all thetools are able to fit into their designated casing joints. Otherwise,the top tool will be anchored, but the tools below may be situated abovetheir designated locking points and unable to anchor. In this, theconveyance that is used for such deployment of a tool array is cable.

In some embodiments of the present disclosure, the conveyance comprisestubing having a cradle for removably retaining the acoustic tool on thetubing for deployment of the acoustic tool in a borehole. The toolcomprises three standoffs and a spring-actuated locking arm located onthe outside of the tool housing; and the tool retainer comprises a slideand a groove located on an inner surface of a borehole casing joint,wherein the tool locking arm is structured and arranged to be extendibleto contact the slide of the casing joint as the tubing is lowered in theborehole so that the locking arm locks into the groove of the casingjoint such that the tool is stabilized and is locked to the boreholecasing by the engagement of the tool locking arm and the casing jointgroove to deploy the tool at a predetermined location and orientationrelative to the subterranean formations. The tubing cradle is configuredsuch that the acoustic tool is disengaged from the cradle afterdeployment for acoustic isolation.

In another embodiment of the present disclosure, the tool comprises anouter jacket; and a plurality of standoffs, a slide and a groove locatedon the jacket. The tool retainer comprises a projection attached to aninner surface of a borehole casing. In some embodiments, three standoffsof the tool jacket are structured and arranged such that the toolretainer projection contacts the tool jacket slide as the tool islowered in the borehole so that the projection locks into the groove ofthe tool jacket to deploy the tool at a predetermined location andorientation relative to the subterranean formations.

In some embodiments of the present disclosure, the system furthercomprises an array of receivers configured or designed to be located inan adjacent borehole traversing the subterranean formations. In certainembodiments herein, the system may be configured for crosswell dataacquisition and/or for monitoring fluids injection into the subterraneanformations through an injection well.

In other embodiments of the present disclosure, the system furthercomprises a seabed cable having an array of spaced receivers configuredor designed to be located at a seabed; and the system is configured formarine data acquisition. The acoustic tool may comprise a bottom holeassembly including the at least one of a seismic source and a seismicreceiver.

The system may comprise a controller section operably connected to theseismic receiver and configured to adjust data acquisition parameters; acommunications interface operably connected to the controller; and aprocessing unit. The seismic receiver may be configured to transmitelectrical signals through the controller section and the communicationsinterface to the processing unit, and the processing unit may beconfigured to perform signal processing using the electrical signalsfrom the receiver.

The present disclosure provides an acoustic tool configured fordeployment in a borehole traversing a subterranean formation. The toolcomprises at least one seismic tool and is configured for movement in aborehole; the at least one seismic tool being configured or designed tobe removably retained by a tool retainer permanently deployed in theborehole so that the seismic tool is deployed at a predeterminedlocation and orientation relative to the subterranean formation.

A method for taking acoustic measurements relating to a subterraneanformation is provided. The method includes deploying a conveyance and anacoustic tool in a borehole traversing the subterranean formation, theacoustic tool comprising at least one of a seismic source and a seismicreceiver; removably retaining the acoustic tool in the borehole so thatthe tool is deployed at a predetermined location and orientationrelative to the subterranean formation, the tool being acousticallycoupled to the borehole; acquiring acoustic measurements; processing theacoustic measurements; and deriving parameters relating to the formationbased on the acoustic measurements.

Additional advantages and novel features will be set forth in thedescription which follows or may be learned by those skilled in the artthrough reading the materials herein or practicing the principlesdescribed herein. Some of the advantages described herein may beachieved through the means recited in the attached claims.

THE DRAWINGS

The accompanying drawings illustrate certain embodiments and are a partof the specification. Together with the following description, thedrawings demonstrate and explain some of the principles of the presentinvention.

FIG. 1 is a schematic representation of one exemplary operationalcontext of the methods and systems of the present disclosure.

FIG. 2 illustrates schematically one exemplary tool for acousticallymonitoring subterranean formations according to the principles describedherein.

FIGS. 3A to 3C illustrate schematically additional exemplary operationalcontexts of the present disclosure with exemplary systems foracoustically monitoring subterranean formations according to theprinciples described herein.

FIGS. 4A and 4B show perspective views of an acoustic tool with aseismic mechanism and a tool retainer according to one embodiment of theprinciples described herein.

FIG. 4C is a step-by-step depiction of the deployment of an acoustictool in a tool retainer according to the principles described herein.

FIGS. 4D and 4E show perspective views of an acoustic tool with aseismic mechanism and a tool retainer according to another embodiment ofthe principles described herein.

FIG. 4F is a depiction of the deployment of an acoustic tool in a toolretainer according to another embodiment of the principles describedherein.

FIG. 5A is a schematic representation of a borehole casing and a casingjoint with a tool retainer according to yet another embodiment of theprinciples described herein.

FIG. 5B is a schematic depiction of the deployment of an acoustic toolin a borehole casing joint with a tool retainer according to anotherembodiment of the principles described herein.

FIG. 5C is a step-by-step depiction of the deployment of an acoustictool array in a borehole according to yet another embodiment of theprinciples described herein.

FIG. 5D is a schematic depiction of the deployment of three levels ofacoustic tools in an acoustic tool array in corresponding boreholecasing joints with tool retainers according to another embodiment of theprinciples described herein.

FIG. 5E is a schematic depiction of the interaction between the lockingelements in the deployment of an acoustic tool in a correspondingborehole casing joint with a tool retainer according to one embodimentof the principles described herein.

FIG. 6 depicts the deployment of an acoustic tool in a borehole toolretainer according to yet another embodiment of the principles describedherein.

FIG. 7 is a block diagram representation of one possible seismic sensorconfiguration according to the principles discussed herein.

FIG. 8 outlines steps in one method according to the present disclosure.

Throughout the drawings, identical reference numbers and descriptionsindicate similar, but not necessarily identical elements. While theprinciples described herein are susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. However,it should be understood that the invention is not intended to be limitedto the particular forms disclosed. Rather, the invention includes allmodifications, equivalents and alternatives falling within the scope ofthe appended claims.

DETAILED DESCRIPTION

Illustrative embodiments and aspects of the invention are describedbelow. It will of course be appreciated that in the development of anysuch actual embodiment, numerous implementation-specific decisions mustbe made to achieve the developers' specific goals, such as compliancewith system-related and business-related constraints, that will varyfrom one implementation to another. Moreover, it will be appreciatedthat such development effort might be complex and time-consuming, butwould nevertheless be a routine undertaking for those of ordinary skillin the art having the benefit of this disclosure.

Reference throughout the specification to “one embodiment,” “anembodiment,” “some embodiments,” “one aspect,” “an aspect,” or “someaspects” means that a particular feature, structure, method, orcharacteristic described in connection with the embodiment or aspect isincluded in at least one embodiment of the present invention. Thus, theappearance of the phrases “in one embodiment” or “in an embodiment” or“in some embodiments” in various places throughout the specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, methods, or characteristics may becombined in any suitable manner in one or more embodiments. The words“including” and “having” shall have the same meaning as the word“comprising.”

Moreover, inventive aspects lie in less than all features of a singledisclosed embodiment. Thus, the claims following the DetailedDescription are hereby expressly incorporated into this DetailedDescription, with each claim standing on its own as a separateembodiment of this invention.

Referring to FIG. 1, as mentioned above it is desirable to use seismicinformation to develop maps or images of underground features using aseismic source 102 generating a seismic signal 104. A downhole seismicsource is used just above the zone of interest, in this case just abovethe movement of the injected fluid, to determine the geologicalcharacteristics of the underground strata in the region surrounding thewell in which the source is placed. Receivers such as accelerometers,geophones, or hydrophones detect these seismic waves after they havetraveled through the underground strata. If the injected gas leaks fromthe reservoir and migrates above the reservoir, such signature may bedetected by sensors 106 deployed in a borehole. After processing, themeasured waves can be used to determine the characteristics of thereflecting surfaces in the strata through which they have traveled.

In a first measurement technique, the receivers 106 are placed on thesurface. In a second measurement technique, the receivers are placed inwells which are different from the well in which the source is located.This technique is known as crosswell or interwell seismic. Finally, thereceivers may also be placed in the same borehole as the source.

The seismic device, i.e., a source and/or a receiver, is usuallysuspended from a cable which also conveys from the surface the power tooperate the device and to the surface various signals from the seismicdevice. Source 102 can be any of a plurality of source types including,but not limited to, a vibrator such as disclosed, for example, in U.S.Pat. No. 4,709,362, an electrical hammer source, a small airgun that isimpulsive and relatively widebanded, and piezoelectric elements that areswept in frequency in a manner similar to surface vibrators, amongothers that are known to persons of skill in the art for the purposesdescribed herein.

The signal 104 propagates throughout the formation 112 to a feature ofinterest such as reservoir 108. While part of signal 104 generallycontinues to propagate through the point 108, some of the energy will bereflected back towards the receivers 106. This receiver in oneembodiment may be a geophone with a high sensitivity to seismic signals.As used herein, the terms “receiver” and “sensor” include any suitabledevice that is configured for detection of source signals and associatednoise for the purposes described herein. The terms “hydrophones” and“geophones/accelerometers” include optical or MEMS devices suitable fordetection of source signals and associated noise according to theprinciples described herein.

A clock measures the time of generation of the seismic signal 104 andthe time of receipt of the direct and reflected signal at receiver array106. Using this time, it is possible to image the feature of interest.The velocity of the signals through the formation may vary depending onthe location, and without an accurate velocity profile, it is difficultto create a reliable image of underground features surrounding theborehole.

As depicted in FIG. 1, the feature of interest may be a reservoir 108into which water or gas is injected via a wellbore 110. In such asituation, it is desirable to monitor the movement of the injectedwater/gas front into the reservoir 108. By appropriate time lapseacoustic measurements it is possible to determine, for example, the oilreplaced by the injected fluid, and location of the remaining oil in thereservoir 108.

Time lapse seismic techniques utilize repeated seismic surveys in thesame area with an interval of a few months to a few years to monitor,for example, the production of hydrocarbons from subterraneanreservoirs. The replacement of oil by water for example causes smallchanges in the acoustic velocity in the reservoir, and the changes maybe observed by the change in the reflection coefficients. In this, thetransit time changes by only a fraction of milliseconds. For example, ifa change in transit time is 0.1 milliseconds, this amount corresponds to0.25 meters/second in an acoustic velocity of 2500 meters/second. Toobserve such small changes, a source and a receiver have to be placedwith an accuracy that is within a fraction of 0.25 meters. It is notpractical to repeatedly deploy a downhole tool for such seismicmeasurements with such accuracy by wireline in a conventional fashion.In addition, it is not certain that the redeployed tool will be orientedin the same direction as it was in the previous deployment.

Such measurements are used to enhance recovery of hydrocarbons fromsubterranean reservoirs. Such measurements may also be utilized tomonitor subterranean reservoirs for purposes of CO₂ sequestration andwater resources. Appropriate data acquisition and processing instruments114 may be provided at the surface, or at a remote location, asdesirable or necessary.

FIG. 2 shows one possible tool configuration that may be used in thecollection of acoustic measurements throughout the borehole according tothe principles described herein. One aspect of the device describedherein is a seismic tool 202 that is deployed in a cased borehole 200with a conveyance such as a wireline 204. Cement 208 is filled in theannulus between the casing 200 and the formation 112 to provide stablecoupling between the formation and the casing. The seismic tool 202 maybe any combination of a seismic source and/or seismic receiver, and isremovably retained in a tool locking mechanism or retainer 206 so thatgood acoustic coupling between the casing and the seismic instrument isestablished. Two or more tools may be used simultaneously in the sametool string. The present disclosure contemplates application of theprinciples herein to various areas, such as wireline, permanentmonitoring, hydro-fracture monitoring, production logging, among others.In this, the systems disclosed herein may be deployed on land or in thesea.

In FIG. 2, borehole 200 may be a previously drilled well, such as aproduction well or a monitoring well, with tools 202 that is used togenerate and/or sense seismic signals. Although one tool is depicted inFIG. 2, a series of tools may be provided as desirable or necessary. Inthis, in addition to seismic devices additional measuring devices may beprovided in additional tools for purposes of measuring various formationproperties such as, for example, resistivity, fluid properties,pressure, temperature, among others that are known to those skilled inthe art. The seismic device 202 may be any type of suitable seismicinstrumentation for generating and/or receiving the desired signals. Thegenerated signals propagate through the formation 112, and some signalsreach sensors 106 (note FIG. 1) having one or more receiving device fordetecting the seismic signals. The sensor arrangement and the associatedreceiving devices may be used as the primary apparatus for collectingthe acoustic measurements, as described in greater detail below.

In one embodiment, a suitable cable 204, for example, a wireline,slickline, or other conveyance that is configured for data telemetry, isprovided for communication uphole with a controller tool 114 on thesurface of the borehole (note again FIG. 1). The analysis tool 114 maybe a stand alone, or may be integrated into a field vehicle.

According to the principles described herein, the tool section(s) may bemoved through the borehole 200 by a winch (not shown), via a suitablearrangement. A device may be used to record the depth of the section202. In one embodiment, the section 202 may be lowered to apredetermined depth in the borehole 200 and then the winch pulls theconveyance 204, and thus the section 202, up through the borehole 200.

In some aspects of the present disclosure depicted in FIG. 3A, avibrator source 302 may be deployed in a well or pit 304 having depthfrom about 30 m to 100 m so that the source is located below theweathered zone, which can highly attenuate and slow down thetransmission of seismic energy into subsurface formations. The seismicsystem 300 may comprise a hydraulic and/or an electro-mechanicalactuation system 306 and a cable system 308 so that the vibrator 302 maybe deployed for active permanent or semi-permanent reservoir monitoring.The frequency and force of the source system may be controlled by thecontroller system 306.

In some embodiments, a seismic device, such as a vibrator or a geophone,has an actuation system, an environment proof cable system, and acontroller system. The present disclosure contemplates that in someembodiments the actuator system may operate based on a program providedby the controller system. In some aspects, the seismic system has amechanical anchoring apparatus to maintain the seismic device in thesame position and orientation, and with the same coupling, over repeatVSP surveys. In aspects herein, the locking or retaining system may bepermanently installed in a well, for example, by cementing, for purposesof long term monitoring of subterranean formations. It is envisionedthat a vibrator actuator system may be designed or configured to vibratein a desired mode such as a broadband vibration from low to highfrequencies.

In one embodiment, the environment proof cable system operates to sendcontrolled electrical power from the controller system to the vibratoractuator system according to a programmed vibration sweep. Thecontroller system operates to generate controlled electrical power forthe vibrator actuator system according to the programmed vibrationsweep. The function may be performed by the controller system itself, orby a separate computer system. The seismic signals recording system maybe connected to the controller system to initiate the start of thevibration, or both systems may be synchronized according to GPS time. Areference sensor (not shown) is located at the downhole source tomonitor the source signature, and the sensor signal is transmitted tothe recorder. The reference signal is used to compute seismic data.

It is envisioned that the aforementioned vibrator actuator system may bedeployed in an oil well and/or a pit below the weathered zone or thehighly attenuating formations near the surface. In this, the energygenerated by the vibrator has an ideal spherical divergence and can betransmitted to the subsurface structures without massive energy loss anddistortions. Furthermore, the buried vibrator may be installed in theoil well and/or pit using different methods to function as a permanentor semi-permanent seismic source. Methods of installation disclosedherein provide an ideal acoustic coupling between the vibrator and theborehole formations.

As previously described, a conventional surface vibrator providesseismic energy at the surface so as to transmit a programmed seismicenergy or seismic sweep into the subsurface for seismic surveying.However, most of the energy that is generated on the surface isconverted to undesired ground roll, and less energy is transmitted tothe earth structure. Due to the weathered zone near the surface thegenerated seismic energy is highly attenuated, in particular, the highfrequency energy. In consequence, a conventional vibrator has togenerate a huge amount of force using an electrically controlledhydraulic system. In addition, there is significant distortion of theseismic energy by surface condition with the distortion increasing whenvibrating at the same place i.e., the same base plate position, for along period of time. A conventional vibrator requires a large truckmaking it unsuitable as a permanent seismic source. The acoustic wavesgenerated on the surface have to travel through the low velocityweathered zone and this causes significant delay in the travel time,which causes ambiguities in interpretation of the data. In contrast,downhole vibrators of the type proposed herein may be deployed below theweathered zone to transmit the desired seismic energy to subsurfaceformations without a major loss in energy and distortions by theweathered zone and the surface terrain.

Downhole vibrators, such as the type described above, may be used asseismic sources at transition zones, such as a swamp or shallow water,since heavy surface vibrators are unable to effectively operate intransition zones.

In some aspects herein, the vibrator may be installed in a well bycementing to operate as a seismic source. In this, cementing providesideal acoustic coupling between the vibrator and subsurface formations.It is envisioned that the actuator system may be installed using severalmethods. For example, the vibrator may be latched inside a cemented welland/or pit so as to be retrievable.

The seismic signal recorded by a seismic sensor represents the actualvibration generated by the vibrator so that the signal can be used formore accurate vibrator control using a feedback method and/or for crosscorrelation purposes with the seismic signals recorded by geophone(s)either at the surface or in the borehole or by simultaneously recordingat both locations. The same signal may be used for quality control (QC)purposes by comparison with a pilot sweep that is generated by thecontroller system. Vibration delay and vibration phase may be monitoredin real time. The seismic sensor may be an accelerometer, a geophoneand/or a hydrophone. However, a hydrophone would require water/fluid inthe well and/or pit, and would need to be lowered from the surface atleast for a few meters. A monitoring sensor may be provided on top ofthe actuator assembly or as a separate sensor in the well and/or pit.

FIG. 3A is a schematic representation of one possible configuration forseismic data acquisition according to the present disclosure. In FIG.3A, a vibrator 302 deployed in a borehole 304 has a controller system306 comprising a controller PC 310; a controller interface 312; and apower inverter 314. The controller PC 310 is programmed to initiate arequired vibration sweep of the vibrator including frequency contents,force, duration, linearity, taper and modulation for a low signal tonoise (SN) ratio. The controller PC issues a vibration start command tostart the vibrator at a programmed timing in a master mode, and monitorsreal-time QC of the actual signal and the system health during theproduction period. The PC can also receive the start command from theseismic signal recording system 316 through a timing signal cable and/ora radio modem 318 in a slave mode. The system clock of the controller PC310 can be automatically synchronized to a GPS clock 320 when a GPSreceiver is connected to the system 300. The controller interface 312has an interface to the controller PC 310, the power inverter 314, theGPS receiver 320, the signal cable from the seismic signal recordingsystem 316, and the radio modem system 318. The controller system alsoprovides a fail-safe system in case of any malfunction of the seismicsystem such as an electrical failure.

The downhole source 302 may be deployed in the borehole 304 usingconventional techniques. For example, a centralizer/packer (shown as adark ring around the downhole source 302) may be used to position thesource 302 in the borehole 304. In this, the source 302 may have asingle centralizer/packer located, for example, in the middle of thesource as depicted in the exemplary embodiment of FIG. 3A, or may have adual centralizer/packer assembly located, for example, at the top andbottom areas of the source 302. The centralizer/packer assembly isconfigured or designed to set the downhole source 302 in the well sothat the source is able to provide stable and repeatable sourcesignatures. Since centralizer/packer assemblies are known to thoseskilled in the art, they are not described in detail in the presentdisclosure. For example, centralizer/packers such as used withSchlumberger's Modular Formation Dynamics Tester (MDT) tool and/orSchlumberger's Mechanical Plug Back Tool (MPBT) may be used fordeploying and securing the downhole source according to the presentdisclosure.

The power inverter 314 is a power supply to the vibrator actuator thatis accurately controlled with respect to frequency. The power invertergenerates the required power according to a programmed sweep commandedby the controller PC 310. The target controlled frequency range is fromabout 10 to about 500 Hz and can be optimized according to the type ofthe survey and the survey environment. The power inverter also has anelectrical feedback system to accurately control the vibrator actuator.

FIGS. 3B and 3C depict some additional exemplary techniques fordeploying seismic devices, such as seismic sources and/or receivers, ina borehole according to the principles described herein.

In FIG. 3B, a seismic tool is deployed in, for example, a drillpipe 422that traverses subterranean formations 424 under a seabed 426. A seabedcable 428 having seismic devices, such as seismic sources or seismicsensors, is deployed at the seabed 426. Typically, it is not possible togenerate shear-waves in the sea since mud at the sea bottom may be toosoft to support a vibrator that is placed on the seabed to generateshear-waves in the subterranean formations. Therefore, a pipe, such asthe drillpipe 422, may be inserted into the mud and a suitable seismicsource conveyed into the pipe to lock it at the bottom of the pipe. Theseismic source may be activated to generate shear-waves.

Furthermore, even with a hard sea bottom a vibrator may be too lightbecause of sea water buoyancy. Therefore, it may be preferable to drilla hole in the sea bottom and to set the seismic source in a lockingmechanism at the bottom of drillpipe. The shear-wave signals may berecorded by using geophones in an ocean bottom cable, orcompressional-waves converted from shear-waves may be recorded usingconventional streamer cables.

FIG. 3C depicts seismic sources deployed in a borehole with a drillpipe452 having a bottom hole assembly 454. A latching or retaining mechanismmay be included in the drillstring above the drillbit. A seismic devicemay be lowered and locked in the drillstring to generate seismicmeasurements. In a highly deviated hole, the seismic device may bepushed down by mud pressure to go into the borehole and to lock with theretaining mechanism. Such an arrangement would replace deploying theseismic device with wireline. The aforementioned technique may beutilized with a seismic source or a seismic receiver.

FIGS. 4A and 4B show perspective views of a seismic tool 500 having, forexample, combinations of seismic source devices and/or seismic sensordevices mounted thereon, and a tool retainer 502 that is configured ordesigned for deployment in a borehole as previously described. The toolretainer or locking mechanism 502 is designed so that tool 500 can beremovably locked into the tool retainer in a manner that the locationand orientation of the tool 500, and the coupling to the borehole, isthe same for multiple deployments of the tool 500 in the borehole.

FIG. 4C shows operation of the seismic tool 500 and the tool retainer502 according to the principles described herein. As the tool 500 isconveyed into the borehole one or more standoffs 504 (three are shown inthe exemplary embodiment of FIG. 4A) that are located on an outerhousing 506 of the tool 500 are brought into contact with a spiral slide508 of the tool retainer 502. As a consequence, the tool 500 is rotated(as depicted in the first three drawings of FIG. 4C) so that a lower oneof the standoffs 504 is aligned with a groove 511 of the tool retainer502. Note the fourth drawing in FIG. 4C. In addition, a taperedprojection 510 located on the tool housing 506 is aligned with a wedge512 that projects from an inner wall of the tool retainer 502. Furtheradvancement of the tool 500 into the borehole causes the lower standoff504 to enter the tool retainer groove 511 so that the tool 500 is lockedinto place in the tool retainer 502. Note the fifth drawing in FIG. 4C.The tool projection 510 contacts the wedge 512 so that tight contact isestablished between the tool standoffs 504 and the tool retainer 502 foracoustic coupling with the borehole.

As previously mentioned above, the tool retainer may be cemented at thebottom of the borehole casing so that acoustic coupling is establishedwith the borehole. Also, the housing of the tool may be designed so thatthe tool slips easily into the tool retainer without the possibility ofjamming.

FIGS. 4D to 4F show another possible embodiment of the seismic tool andthe tool retainer. In the present embodiment, a tool jacket 514 encasesthe outer housing 506 of the tool 500 and, in addition to the toolstandoffs 504, a bidirectional slide 516 and groove 518 are structuredand arranged on the tool jacket 514. In contrast with the embodiment ofFIG. 4A, in the present embodiment the tool retainer is a triangularshaped projection 520 that is attached to an inner wall of the boreholecasing 522 in a manner that the tool retainer 520 is acousticallycoupled with the borehole. The projection 520 of the borehole casing 522is configured or designed so that it co-acts with a wedge shaped surfaceof the groove 518 of the tool jacket 514 so that the elements are lockedtogether by gravity force acting on the tool 500 to force or push thetool standoffs 504 against the borehole casing wall for securing andcoupling the tool to the borehole.

As the seismic tool 500 is conveyed into the borehole the standoffs 504position the tool 500 in the borehole so that the tool retainerprojection 520 contacts the bidirectional slide 516 causing the tool 500to rotate in the borehole so that the tool retainer projection 520 isaligned with the groove 518 in the tool outer jacket 514. Since theslide 516 is bidirectional the tool 500 will rotate in the clockwise orcounterclockwise direction depending on where contact is made with thetool retainer projection 520. Once aligned, the tool retainer projection520 locks into the wedge shaped tool jacket groove 518 so that the tool500 is located and oriented, and acoustically coupled to the borehole.As previously mentioned, the tool retainer projection 520 and the tooljacket groove 518 have corresponding contact surfaces that are taperedso that as the tool retainer projection 520 fits into the tool jacketgroove 518 the tool 500 is pushed as indicated by the arrow in FIG. 4Fso that the standoffs 504 are in contact with the casing 522 and thetool is acoustically coupled with the borehole. In the embodiments ofFIGS. 4A to 4F, surface activation is not required to deploy the seismicdevices, i.e., the deployment is self-activating as the tool or toolsare lowered in the borehole. As the tools descend in a borehole, thetools are oriented, and are anchored by the force of gravity with thesupport of the slides and the wedges.

In the preceding description, a plurality of standoffs have beendescribed. However, the present applicants have recognized that aconfiguration of three standoffs arranged in a triangular configurationwith the apex pointing downward would provide secure coupling andsupport to the acoustic tool in the borehole. In this, various priortechniques for securing tools in a borehole are susceptible to looseningdue to thermal changes and/or due to vibration. Since secure positioningand acoustic coupling are important for acoustic measurements in aborehole, the present arrangements of three standoffs in combinationwith other co-engaging elements described herein provide the desiredresults. Furthermore, the preceding embodiments do not need anyactivation of the locking mechanisms from the top of the borehole. Theacoustic tool is deployed by gravity using an appropriate conveyance sothat the tool is lowered into the borehole and oriented by, for example,a spiral slide to self-lock into the retaining mechanism in theborehole. A wedge type element engages a corresponding action point sothat through the action of gravity the wedge and the correspondingelement are tightly engaged thereby pushing the tool into tight contactwith the borehole casing. In retrieving the acoustic tool, by pulling onthe conveyance the deployment process is reversed and the tool isdisengaged from the retaining mechanism in the borehole.

FIG. 5A is a schematic representation of a borehole casing 522 and acasing joint 524 with a tool retainer according to yet anotherembodiment of the principles described herein. FIG. 5B is a schematicdepiction of the deployment of an acoustic tool 500 in a borehole casingjoint 524 with a tool retainer according to another embodiment of theprinciples described herein. As depicted in FIGS. 5A and 5B, the casingjoint 524 is designed to removably retain the acoustic tool 500 bylocking the tool to the borehole. The casing joint 524 has a spiralslide 526 and an associated locking groove 528 that are located on aninner surface of the casing joint 524. For example, the casing joint maybe machined to prepare the slide and groove configuration for removablyretaining the acoustic tool. The specially configured casing joints maybe deployed in a borehole casing at appropriate locations at which theacoustic tools are to be located for acoustic measurements so that theacoustic tools may be repeatedly deployed at the same location, and withthe same orientation and acoustic coupling with the borehole.

As depicted in FIG. 5B, the acoustic tool 500 is configured with alocking arm 530 on the outer housing of the acoustic tool 500. Thelocking arm 530 is extendible with, for example, a spring 532 andactuator 534 mechanism that extends and retracts the locking arm 530. Itis noted that locking groove 528 has a sloping top surface so that thelocking arm 530 can be extracted from the groove 528 when the tool 500is retrieved from the tool retainer by pulling it upward in theborehole. Note FIG. 5B. The locking arm 530 may be activated from thesurface using any suitable activation technique such as by wireconnection, hydraulic connection and/or annulus pressure change usingrupture disks. Such techniques are well known to those skilled in theart.

In the tool deployment that is depicted in FIG. 5B, the acoustic tool500 is lowered into the borehole till it reaches the target depth atwhich the specially designed casing joint 524 is located. At just abovethe target depth, the locking arm 530 is activated by, for example,surface activation of the spring 532 and actuator 534 mechanism. Sincethe locking arm 530 is spring loaded, the arm 530 slides down the casing522 (note FIG. 5A) as it descends in the casing 522. The locking arm 530opens to its extended position when it reaches the spiral slide 526 inthe casing joint 524. The locking arm 530 enters the slide 526 and thetool 500 is turned to the desired orientation. When the locking arm 530reaches the alignment part of the groove 528, the tool 500 goes downvertically until the locking arm 530 reaches the bottom of the lockinggroove 528. The force of gravity pushes the locking arm 530 in theupward direction and the force acts to further open the arm 530 to lockthe tool 500 to the casing wall. In this, secure contact is maintainedvia the standoffs 504. Note again FIG. 5B.

FIG. 5C is a step-by-step depiction of the deployment of an acoustictool array 540, 542, 544 in a borehole according to yet anotherembodiment of the principles described herein. Each tool 540, 542, 544in the array is configured as described above in connection with FIGS.5A and 5B, and has a corresponding casing joint 524 of the casing 522,which also is configured as previously described above. The tools 540,542, 544 of the acoustic tool array are deployed as previously describedabove in connection with FIG. 5B.

The cable separation between adjacent tools in the array is slightly,for example 5%, longer than the separation of the designated casingjoints so that there is slack in the excess cable to prevent acousticnoise propagation along the cable. In addition, the longer cable betweenadjacent tools is needed to avoid the uppermost tool getting into thegroove of the top casing joint that is designated for it while the lowertools are unable to reach the designated casing joint grooves due toinsufficient cable length.

The locking arms 530 of the tools 540, 542, 544 are maintained in aclosed position while the tool array is running in the hole. Then, thelocking arms 530 are opened by, for example, an appropriate command fromthe surface when the tools 540, 542, 544 are situated just above theirdesignated grooves 528 of the casing joints 524 so that each tool 540,542, 544 is locked into its designated groove 528. With thisarrangement, the bottom tool 544 is prevented from getting into theuppermost groove 528 which is designated for the tool 540.

Referring also to FIGS. 5B and 5E, after a locking arm 530 is situatedon the bottom of its designated groove 528, the force of gravity pushedthe associated tool 500, 540, 542, 544 down, and the locking arm 530operates to push the tool 500, 540, 542, 544 to the casing wall to lockthereto. Note FIGS. 5B and 5E. In this, the locking force of the lockingarm 530 is determined by the angle of the locking arm 530 and gravity.Note FIG. 5E. As indicated in FIG. 5E, the angle of the locking arm θmay be selected so as to be less than 90 degrees. When retrieving thetools by pulling the conveyance out of the borehole, the tools are movedup and the locking arms 530 are pulled out from their designated grooves528 by the angle of the arms 530. Although some exemplary embodimentsdepicted in FIG. 5B show the groove 528 with a tapered top surface, ataper may not be needed since the locking arm has an angular surface.FIG. 5D depicts another method of anchoring each acoustic tool 540, 542,544 of the acoustic array in FIG. 5C in its designated casing joint 524.Although FIG. 5D depicts the deployment of three levels of acoustictools 540, 542, 544 in an acoustic tool array in corresponding boreholecasing joints 524 with tool retainers, it is contemplated by the presentdisclosure that any number of tools may be deployed according to theprinciples described herein, as desirable or necessary.

As depicted in FIG. 5D, each tool 540, 542, 544 of the tool array has,in addition to a spring-actuated locking arm 530, an additional supportarm 536 that supports a corresponding, sized clamping pad 537, 538, 539.Each clamping pad 537, 538, 539 corresponds to one of the tools 540,542, 544 of the tool array and is sized so that the lower tool 544 has alonger pad 539 and the upper tool 540 has a shorter pad 537. Similarly,each locking groove 528 is sized to correspond with the clamping pad537, 538, 539 of the tools 540, 542, 544 of the tool array that isintended to lock into the groove. Note again FIG. 5D.

The length of the arm clamping pads 537, 538, 539 of the tools 540, 542,544 and groove 528 lengths are chosen so that a pad 537, 538, 539 canonly fit into the target groove 528, i.e., the top pad 537 is theshortest, the middle pad 538 is intermediate size, and the bottom pad539 is the longest. In this, as the tools 540, 542, 544 of the toolarray descend, with corresponding locking arms 530 opened by springactuation, the uppermost and intermediate casing joints 524 have theshorter grooves 528 while the lowermost tool 544 has the longest pad 539so that the pad 539 of the tool 544 is unable to settle into the grooves528 of the uppermost and intermediate casing joints 524. The pad 539 isable to enter only the longest groove 528 of the lowermost casing joint524 and so on for the other tools 540, 542 of the tool array. Aspreviously described above, with the present configuration the toolarray may be deployed without activation from the surface.

Although different size arm clamping pads 537, 538, 539 of the tools540, 542, 544 have been described above to ensure that the locking arms530 lock into the designated grooves 528, the present disclosurecontemplates other mechanisms and techniques for accomplishing the sameresult. For example, a key arrangement might be used to ensure that thecorrect locking arm 530 locks into the designated groove 528. Moreover,the locking arms 530 also could be maintained in the retracted positionstill such time that the correct tool 540, 542, 544 is situated justabove its designated groove 528, and then the locking arms 530 could beextended to fit into their designated grooves.

Furthermore, as depicted in FIG. 5C, the present configuration providesfor conveyance cable slack between adjacent tools 540, 542, 544 of thetool array. For example, conveyance cable length may be 5% longer thanthe distance separating adjacent casing joints 524. In this, cable slackis provided to make sure that there is enough length of cable so thatall the tools 540, 542, 544 sit on bottom of their designated grooves528 and the tools are anchored, and to prevent noise propagation throughthe conveyance cable under tension. The present configuration providesfor cable slack to attenuate noise in the wireline deployment of anarray of acoustic tools.

FIG. 6 depicts the deployment of an acoustic tool in a borehole toolretainer according to yet another embodiment of the principles describedherein. In FIG. 6, tubing 548, such as production tubing, is used asconveyance for deploying an acoustic tool 546 in a borehole casing 522.A cradle 550 is attached to the tubing 548 to removably retain the tool546 for deployment according to the principles described herein. Aspreviously described above, casing joint 524 is provided with, forexample, a spiral slide and locking groove 528 configuration toremovably retain the acoustic tool 546 at a predetermined location andorientation, and acoustically coupled with the borehole. The acoustictool 546 has a locking arm mechanism 552 that is similar to the lockingarm mechanisms described above. The cradle 550 attached to the tubing548 securely conveys the acoustic tool 546 while the tool is descendinginto the borehole.

After the tool 546 is securely locked into the locking groove 528 of thecasing joint 524, the tubing 548 is further lowered so that the cradle550 is detached from the acoustic tool 546 for acoustic isolation.During deployment, as soon as the locking arm 552 is situated in thegroove 528, the tool 546 is lifted from the cradle 550 on the tubing 548to prevent any noise propagating on the tubing 548. As the tool 546 doesnot touch the tubing 548 after deployment, there is acoustic isolation.

The acoustic tool 546 may be retrieved from the borehole by reversingthe process by pulling the tubing 548 out of the borehole so that thecradle 550 “catches” the acoustic tool 546. When retrieving, the tubing548 is pulled upward and the cradle 550 catches the tool 546 at thebottom. The locking arm 552 comes out from the groove 528 by the angleof the arm 552.

The present disclosure includes acoustic systems for monitoring oiland/or gas production, deployment of such systems, andmodeling/measurement evaluation. To achieve long term production,changes in key reservoir parameters must be monitored in order to makeappropriate decisions for well intervention.

The present disclosure provides an integrated measurement system toevaluate different physical properties of subterranean formations. Incertain embodiments, permanent or semi-permanent acoustic crosswellmonitoring systems may be provided in accordance with the presentdisclosure to investigate subterranean formations. A permanentinstallation may include, for example, one or more downhole acousticsource in the production well and a permanent/semi-permanent acousticsensor array in a monitoring well, or vice versa. Note again FIG. 1.

The acoustic sources of the present disclosure are designed forexcellent repeatability and to provide broadband signals. In this,generation of large high frequency energy is possible by increasing thesignal duration and by the improved coupling. Several applications areenvisioned including high resolution tomography, time lapse VSP, timelapse crosswell seismic, stress detection monitoring, among others.

In one possible embodiment, acoustic sources are installed in theannulus between, for example, a production tubing and the boreholecasing. In this, acoustic measurements may be acquired during productionby crosswell seismic measurements between the production well and themonitoring well without extracting the production string. Acousticsources that are deployed in this configuration have to be small enoughto fit in the designated annulus.

With respect to time lapse measurements, the acoustic sources of thepresent disclosure are repeatable with positioning error beingeliminated because the retaining mechanisms for the sources are cementedin the casing. In addition, small packaging of the acoustic sourcesprovides for the deployment of multiple sources in one well in a sourcearray configuration.

FIG. 7 shows one example of a sensor section or arrangement according tothe principles discussed herein. The acquisition front end 402 isconnected with the sensor elements described above, as well as theirassociated connections and electronics. For example, the acquisitionsection 402 may include electronics suitable for the relevant or desiredfrequencies that are to be received by the receiving device. In this,electronics for signal conditioning and digitization may be included asknown to those of skill in the art. The overall operation of the systemis coordinated by controller 404. The controller is capable of adjustingthe acquisition parameters for section 402 and timing the start and endof acquisition, among its other functions. A real time clock 406 may beused to provide the time to the controller for the determination of whena signal is captured and for timing the appropriate collectionintervals. This clock's time is used in concert with the time that theseismic signal is generated so that the travel time can be determined.Information from the controller may be sent to an analysis unit 412. Inone embodiment, an analysis unit may be located at the surface of theborehole (note FIG. 1).

Communications interface 408 may be used to convey the signals outputfrom the controller 404 to communication cable 410, and subsequently toanalysis unit 412. The analysis unit may perform adaptive noisecancellation as well as determination of the signal velocity for eachdata collection. The functions of the analysis unit may be distributedbetween tools at the surface and downhole, as desirable or necessary forthe operations described herein. In certain embodiments of the presentdisclosure, the seismic sources can be activated with the receivers at avariety of depths. This allows the system to ensure that measurementsare taken at specific depths.

Referring to FIG. 8, in a method according to the present disclosure, asource retainer is positioned within a borehole at at least one depth(note flow diagram block 52). A tool is deployed in the borehole and islocated or inserted in the source retainer (note block 54). Acousticdata measurements are acquired at at least one depth in the borehole(note block 56) to provide seismic information of the formation suchthat the measured data relate to different reservoir parameters ofinterest in the formation.

The acquired acoustic data are processed to determine key reservoirparameters (note block 58) relating to, for example, oil production, gasproduction, formation structure, among others.

The embodiments and aspects were chosen and described in order to bestexplain the principles of the invention and its practical applications.The preceding description is intended to enable others skilled in theart to best utilize the principles described herein in variousembodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims.

What is claimed is:
 1. A system for taking acoustic measurements relating to subterranean formations traversed by a borehole, comprising: at least one acoustic tool comprising; an outer surface; two or more standoffs located on the outer surface; and a first projection located on the outer surface; a conveyance to deploy the acoustic tool in the borehole; a tool retainer permanently deployed in the borehole to removably retain the acoustic tool at a predetermined location and orientation relative to the subterranean formations, comprising; a slide leading to a groove; and a second projection located on the tool retainer; wherein one of the two or more standoffs of the outer surface of the acoustic tool contacts the slide during deployment and engages the groove, orienting the first projection to contact the second projection and acoustically couple another of the two or more standoffs and the tool retainer; a computer in communication with the acoustic tool; and a set of instructions executable by the computer that, when executed: process the acoustic measurements; and derive parameters relating to the formation based on the acoustic measurements.
 2. The system of claim 1, wherein the acoustic tool and the tool retainer are configured or designed such that the acoustic tool is deployed in or removed from the tool retainer by the downward or upward movement of the acoustic tool by the conveyance.
 3. The system of claim 1, wherein the tool retainer is configured or designed to be located at the bottom of a borehole casing.
 4. The system of claim 1 where the first projection is a wedge.
 5. The system of claim 1 where the second projection is a wedge.
 6. A system for taking acoustic measurements relating to subterranean formations traversed by a borehole, comprising: at least one acoustic tool comprising; an outer surface comprising a slide leading to an angled groove; two or more standoffs located on the outer surface; a conveyance to deploy the acoustic tool in the borehole; a tool retainer configured or designed for permanent deployment in the borehole to removably retain the acoustic tool in a predetermined location and orientation relative to the subterranean formations, comprising a projection; wherein the projection contacts the slide and engages the groove during deployment, acoustically coupling the two or more standoffs with the tool retainer.
 7. The system of claim 6, wherein the system is configured for monitoring fluids injection into the subterranean formations through an injection well.
 8. The system of claim 6 wherein at least a portion of the projection is an angled surface relative to deployment.
 9. A method for taking acoustic measurements relating to a subterranean formation comprising: deploying an acoustic tool via a conveyance in a borehole traversing the subterranean formation; removably retaining the acoustic tool at a predetermined acoustic coupling location and orientation relative to the subterranean formation; acoustically coupling the acoustic tool and a tool retainer via standoffs and one or more projections; detecting seismic signals; processing the acoustic measurements; and deriving parameters relating to the formation based on the acoustic measurements.
 10. The method of claim 9, further comprising locating an array of receivers in an adjacent borehole traversing the subterranean formations; and acquiring crosswell seismic data.
 11. The method of claim 9, further comprising monitoring fluids injection into the subterranean formation through an injection well.
 12. The method of claim 9, wherein removably retaining the acoustic tool further comprises: locating a tool retainer permanently in the borehole; engaging one of two or more standoffs located on an outer surface of the acoustic tool with a slide leading to a groove located on the tool retainer; wherein the engagement of the one of the two or more standoffs contacts a first projection on the outer surface of the acoustic tool with a second projection on the tool retainer, acoustically coupling another of the two or more standoffs and the tool retainer.
 13. The method of claim 12 wherein at least one of the first projection and the second projection is an angled wedge.
 14. The method of claim 9, wherein removably retaining the acoustic tool further comprises: locating a tool retainer comprising a projection permanently in the borehole; engaging the projection with a slide leading to an angled groove located on an outer surface of the acoustic tool; wherein the engagement of the projection and the angled groove of the acoustic tool acoustically couples two or more standoffs located on the acoustic tool and the tool retainer.
 15. The method of claim 14 wherein acoustic receivers of the acoustic tool received seismic signals via the two or more standoffs. 